Solid electrodes of lead oxide are mechanically weak and are thus of limited practical utility. Use is therefore frequently made of an inert metallic support, such as a plate or a grid, which is coated with lead oxide PbO.sub.2, preferably by electrolytic deposition. Such a support advantageously consists of titanium; however, firmly adhering coatings of lead oxide have heretofore been achieved on titanium bodies only by relatively complicated and costly processes.
In commonly owned U.S. patent application Ser. No. 468,804 filed May 10, 1974, now U.S. Pat. No. 3,935,082, there has been disclosed a process for manufacturing electrodes of this nature. According to that prior patent, a titanium body is cleansed in a hot mordanting or pickling solution of aqueous oxalic acid, this operation beIng followed by prolonged immersion in the same bath in which a titanium-oxalato complex has been dissolved. Thereafter, the titanium body is anodically connected against a suitable counterelectrode in an electrolyte containing the ions of lead (II) in the presence of a Pb(II) salt of an amido, imido, nitrido or fluoro sulfate or phosphate. A final treatment stage may comprise prolonged immersion in a weakly alkaline medium.
Though the process described in the prior application has been practiced successfully, and is also fully reproducible, there has as yet not been established a comprehensive theory which would allow the development of a variety of techniques for the formation of different types of PbO.sub.2 deposits firmly adhering to the supporting titanium body.